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At autocross yesterday I noticed the radiator fans Veedubs automatically switch on and remain on until the temp sensor says its cool. Now, I don't need anything nearly that complex... just a switch will do. But I want to be able to run them while the car is off. Anyone know how to rig this up (guessing battery power)? I need them to still come on automatically when the car deems necessary, but I want control over it too.

 
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it seems that if you just knew what wires it wouldent be all to hard
just run another wire to power and put a switch in the regular stock line... just a quick thought

 
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if you want to force your fans on after shutdown, turn the key to ACC, turn on the interior fan, and hit the A/C button. it probably helps with the heat soak-back problem on really hot days following spirited driving. it'd be nice to rig up a system that runs the fans after shutdown thermostatically, or better yet, on a timer. somebody more wire-savvy than me should make a DIY .
-jro

 
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kinda like a turbo timer? or when the car sits in the hot sun it senses it so the fans come on? that would rule

 
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look for the fuse in the fuse box under the hood... and just run a switch to the relay...

 
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I just cut the wire harness off and spliced in 12 gauge wire run to a switch by the power outlet thats ubove the cup holder. I can have the fans on with the car off, but the battery went dead waiting to run at the track because there was a wreck and they had to clean it up. If you do it make sure the fans run in the right direction when you hit the switch

 
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But when the engine is off, the waterpump isnt circulating the coolant. All you'd be doing is cooling off the coolant thats in the radiator...

 
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no, i can feel the fans blowing air on the motor. I was thinking of this same exact thing.

Heres what you do... just tap some 16 (or so) gauge wire into the + wire of the fans (both) and run that wire into the cabin (where you want it) then hook it up to one terminal of the switch, then run a second wire from the second terminal (on that same switch) , run it back out to the engine bay and onto a + terminal of the battery or you could use the fusebox. Just dont forget to turn the switch off when you leave your car. I was thinking of this, but its really impractical. Lets say your doing some spirited driving, just have the key turned on to ACC, and turn the FAN dial on along w/ the A/C button. I did this yesterday when i got to the top of a mountain

 
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Don't see whats so bad about that. When I turn the car back on, its going into the engine.
Even when I leave the car idling on the grid, the fans don't always switch on. So the car may be on... and the fans aren't.... I want them to run.
I'll have to get a multimeter out and do some prodding tomorrow.

 
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Wrong. Coolant will continue to circulate in the engine after shutdown due to a phenomenon known as thermosyphoning. Hot coolant in the engine, which is less dense than the cooler coolant in the radiator, rises to the outlet and flows into the radiator. As the hot coolant from the engine cools in the radiator, it moves back into the engine. The cycle continues so long as there is a temperature differential between the engine and the radiator.

It is beneficial to have a fan after shutdown to prevent ‘heat soak-back’. Heat soak-back occurs when the engine heats up everything in under the hood, thereby eliminating the temperature differential between the engine and the radiator. Without a temperature differential, the thermosyphoning effect is non-existent.

All said, coolant WILL continue to circulate throughout the engine so long as there is sufficient airflow through to radiator.
-jro